public static int activityNotifications(List<Integer> expenditure, int d){
        final int size = expenditure.size();
        if(d>=size){
            return 0;
        }
        
        int notifications = 0;
        List<Integer> dList =  expenditure.subList(0,d).stream().sorted().collect(Collectors.toList());
        for(int i=d; i<size; i++){
            int doubledMedian = getDoubledMedian(dList);
            int current = expenditure.get(i);
            if(current >= doubledMedian){
                notifications++;
            }
            Integer firstDay = expenditure.get(i-d);
            dList.remove(firstDay);
            addItemToSortedList(dList, current);
            firstDay = current;  
        }
        return notifications;
    }
    
    final static int getDoubledMedian(List<Integer> sortedList){
        final int size = sortedList.size();
        final int index = size/2;
        if(size%2 != 0){
            return 2*sortedList.get(index);
        }
        return sortedList.get(index-1) + sortedList.get(index);
    }
    
    final static void addItemToSortedList(List<Integer> dList, int newItem){
        int index = Collections.binarySearch(dList, newItem);
        if(index < 0){
            dList.add(-(index+1),newItem);
            return;
        }
        dList.add(index,newItem);
    }